Novel transfer elements from porous alkenyl aromatic films

ABSTRACT

This invention relates to transfer elements useful in providing non-smearing imprints which are sharp, dark, well defined prints. The transfer elements comprise a base of an alkenyl aromatic resinous film having an ink receptive, porous matte finish comprising an ink receptive resinous polymer having distributed therein a relatively non-volatile compatible polar vehicle based ink. For example, a nigrosine based color developed by a fatty acid, alone, or in combination with an additional non-reactive vehicle.

United States Patent [191 Rosendale et al.

[ Sept. 23, 1975 NOVEL TRANSFER ELEMENTS FROM POROUS ALKENYL AROMATIC FILMS [75] Inventors: William Lee Rosendale, Miamisburg; Ardyth Dale Lakes, Dayton, both of Ohio [73] Assignee: Monarch Marking Systems, Inc.,

Dayton, Ohio [22] Filed: Sept. 27, 1974 [21] Appl. No.: 510,087

[52] U.S. Cl. 428/320; 427/150; 427/153; 428/409; 428/914 [51] Int. Cl. B41C l/06; B41M 5/02 [58] Field of Search l17/36.1, 36.2, 138.8 UA; 161/160, 164, 406, 402

[56] References Cited UNITED STATES PATENTS 3,027,275 3/1962 Park 117/1388 UA Park 117/1388 UA Baum 117/364 Primary Examiner-William J. Van Balen Attorney, Agent, or Firm-.lon|es, Tullar & Cooper [5 7] ABSTRACT This invention relates to transfer elements useful in providing non-smearing imprints which are sharp, dark, well defined prints. The transfer elements comprise a base of an alkenyl aromatic resinous film having an ink receptive, porous matte finish comprising an ink receptive resinous polymer having distributed therein a relatively non-volatile compatible polar vehicle based ink. For example, a nigrosine based color developed by a fatty acid, alone, or in combination with an additional non-reactive vehicle.

20 Claims, 4 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of 2 3,908,063

FIG.

US Patent Sept. 23,1975 Sheet 2 of2 3,908,063

FIG. 2 X 2040 FIG. 3 X 5100 NOVEL TRANSFER ELEMENTS FROM POROUS ALKENYL AROMATIC FILMS DISCUSSION OF THE PRIOR ART Many various types of transfer elements have been proposed in the art. Most have demonstrated one or more drawbacks, including costs, the use of volatile organic solvents, difficulties in preparing a transfer element, poor handling quality, including narrow ranges of useful temperatures, the quality of the print formed, for example, lack of sharpness due to feathering or poor drying or poor smudge resistance.

The matte finish film base material employed in forming the transfer elements of this invention are known in the art and can be prepared, for example, by the processes described in US. Pat. No. 3,311,497 and 3,027,275, the disclosure of both these patents being hereby incorporated by reference. The matte finish films have been described as possessing surface characteristics suitable for marking with a conventional writing ink.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying FIGURES are photomicrographs of the matte finish base film employed in the examples. The order of magnification is stated in each Figure.

DESCRIPTION OF THE INVENTION It has now been found that transfer elements such as typewriter ribbons and carbon paper, especially useful in automatic data printing devices, can be formed which comprise a thin alkenyl aromatic resinous film having an ink receptive porous matte finish comprising an ink receptive resinous polymer having substantially uniformly distributed across the surface and retained therein a pressure expressible mixture comprising a compatible relatively non-volatile, polar vehicle based ink.

The ink or image forming material chemically can wet the treated polymer surface through attractive surface forces between the ink and the treated polymer surface interfaces and be absorbed into the treated ab sorbent pores or depressions in the base film matte surface. The surface of the absorbed laayer of ink is dry relative to carbon and dye print ribbons used in the impact printing art. When deliberate localized pressure is applied to the polymer film the ink is expressed from the films surface layer to form an image upon an ink absorptive image receiving article such as paper.

The base film materials employed in the transfer elements of the invention may be prepared by treating the surface of a swellable, integral solid alkenyl aromatic resinous film usually having a thickness between about 0.5 to about mils and preferably from about 0.5 to 2 mils. Such a polymer may have an essentially linear and molecular configuration and may generally be prepared from a monomer mixture that contains at least 'about 50 percent by weight of at least one polymerizable alkenyl aromatic compound or monomer having a .general formula Ar- C =CH:

where R is a hydrogen on methyl and Ar is an aromatic radical, usually of the benzene series, of from 6 to 10 carbon atoms (including the carbon atoms in any ring constituent on the automatic nucleus). Thermoplastic, homopolymers and copolyrners of styrene, alphamethyl styrene, ar-methyl styrene (vinyl toulene), the several mono and difluoro styrenes and ar-dimethyl styrene, may likewise be employed.

The alkylene aromatic polymer resin in treated with a mixture comprising an organic liquid medium which is a swelling agent for said alkenyl aromatic resins, having dispersed therein an ink receptive resinous polymeric material, until the surface of the film is swollen by the swelling agent and subsequently removing the volatile components of said mixture from the film.

A wide variety of organic swelling agents may be em ployed in the practice of the invention. Acetone is particularly suitable in preparing the base film. Ketone compounds such as methyliso'butylketone, methylethylketone and the like may also be used with good results. Various solvent mixtures are successfully employed which comprise a swelling agent in the mixture with other swelling agents or substantially inert diluents such as water, alcohol and the: like.

A mixture of swelling agents and non-solvents which is particularly useful to prepare the'base film comprises two parts of ethanol, one part butanol, one part methylisobutylketone, one part ethylacetate and two parts toulene. The choice of a particular swelling agent or mixtures thereof with or without diluents will depend on the particular alkenyl aromatic resin employed, the time of exposure desired and the temperature of the treatment bath. Usually it is most advantageous to employ, for dispersion of the ink receptive resinous polymeric material and subsequent treatment of the alkeynl aromatic resinous film, swelling agents, or swelling agent containing mixtures that boil, under atmospheric pressure, below about C. and above about 40C. The wide variety of polymer resinous materials may be employed as the ink receptive resinous polymric material in preparing the base film. Copolymers prepared from such monomer systems is vinylidene chlorideacrylonitrile, vinylchloride-vin ylacetate, vinylchloridevinylproprionate, vinylchloride-maleicanhydride, vinylchloride-diethylmaleic are typical materials that may be employed. Other suitable copolyrners are prepared from vinylchloride-methylmethacrylate, vinylchloride-ethylacrylate, vinyidene chloride with various methacrylate, acrylate and maleate esters. Also ternary and quaternary copolyrners of the foregoing monomers can likewise be employed. Various esters, such as, for example, condensation products of bisphenols and epichlorohydrin, nitrocellulose, polyvinyl butyral and polyvinylacetals, and also polyester compositions containing an aromatic nucleus as an integral unit in the polymer molecule may also be employed.

The number of the synthetic resinous materials which may be adapted to prepare the base polymer film are varied and have in common the property of accepting conventional writing ink to a limited degree. Any polymeric material is readily determined to be suitable or unsuitable in preparing the base film by the following test:

A synthetic resinous material to be evaluated as molded or solvent cast into a form which has at least one relatively smooth surface. A writing pen containing an ink is drawn across the smooth surface of the polymeric material in a conventional writing manner. If the line left by the pen remains constant in width and shows continuity of the ink film to the unaided eye the material is satisfactory to be employed in treating alkenyl aromatic films to prepare the base materials for this invention. The solubility of the treating resin must be such that it is soluble or readily dispersible in the solvent system employed for matte surfaces with the alkenyl aromatic polymer film. Any commercially available writing ink may be employed in this test. However, the most discriminating of the commonly available writing inks would appear to be a writing ink sold under the tradename of Parker 51.

The film, when treated to become ink receptive, may be simultaneously destatictized by adding to the treating medium an alkali metal salt of a sulphonated alkenyl aromatic resin dispersible or soluble therein. Such salts are usually prepared by the sulphonation and subsequent neutralization of polymers such as polystyrene which have essentially a linear molecular configuration. Such polymers when sulphonated usually contain between about 0.1 to 1.5 sulphonate groups per alkenyl aromatic monomer unit and have molecular weights between about 50,000 and 750,000.

A surface treating solution or dispersion is readily prepared by dissolving the resinous treating material in the solvent system employed to form the matte surface on the alkenyl aromatic resin film. The concentration of the treating resin in the solvent may usually be from about 0.5 to about 5 percent and advantageously between about 0.1 and about 2 percent and beneficially from about 0.2 to about 0.5 percent. Dissolution of the treated resin in the treating medium may be accomplished by any of the conventional methods such as heating with or without agitation, agitation, alone, or mechanical dispersion of the resin throughout the medium by mechanical means such as colloid mills and the like. Frequently, it may be advantageous to form a concentrate of the resinous material in a portion of the treating medium at concentrations of 25 or even about 50 percent based on the total weight of the concentrate.

Alternately, the surface treating solution in a dispersion which would result in the static-free alkenyl aromatic base film is readily prepared by incorporating into the treating medium a concentrate, which may be prepared by first dispersing an aqueous solution of a1- kalinc metal salt of a sulphonated alkenyl aromatic resin in a minor portion of the organic liquid media of the treating composition, and subsequently, diluting to the desired concentration, usually between about 0.1 to about 1 percent based on a total weight of the treating media, and advantageously between about 0.15 to about 0.35 percent based on the total weight of the treating media. An aqueous solution of alkaline metal salts of the sulphonated alkenyl aromatic resin advantageously may be dissolved or dispersed in a portion of the treating liquid, or, if a multicomponent mixture is employed, in a portion of any one or all of the liquid components by employing high speed agitation for a period of time which is dependent on the particular liquid system or dispersing media employed and the molecular weight of the alkaline metal salt of the sulphonated alkenyl aromatic resin.

Generally, it is advantageous to treat the surface at a temperature with the treating media within the temperature range of about 0C. to about 60C. It is frequently desirable to employ a treating range from about 5C. to about 30C. and often times it is beneficial to employ a range of about 5C. to about 15C. A particular temperature which is most beneficial for any specific treating solution or dispersion or any specific alkenyl aromatic resin will depend in part upon the specific characteristics of the swelling agents employed in the treating composition and partly on the swelling characteristics of the alkenyl aromatic resin. Film prepared from high molecular weight and alkenyl aromatic resin generally require a longer time at a higher temperature in contact with a treating composition. Similarly, a highly active swelling agent will require a relatively shorter contact time.

In the method of preparing the base film, various methods may be employed to apply the treating composition to the surface of the alkenyl aromatic resin film. It is frequently advantageous to dip the film in a bath of a suitable treating composition; whereas alternately, sheets or films may be treated by dipping, rolling, spraying or brushing the treating media or composition onto the surface of the polymer.

The volatile components of the treating composition are readily removed from the treating surface by evaporation. Frequently, exposure of the treated surface to air is sufficient but often, particularly when continuous, an air blast directed toward the surface to be treated is particularly advantageous.

While a particular method of preparing the matte finish for base films has been described, obviously films having essentially the same characteristics may be employed to yield equivalent beneficial results.

The matte finish base film amenable for use in this invention can be described as film having a surface which can be described as an irregular fibrous appearing network of open cells linked three dimensionally. The size and geometric shape of the pores in the network are non-uniform and sponge-like in appearance, as shown by the accompanying drawings which are scanning electron micrographs of a treated polystyrene structure which illustrates the physical non-uniformity of shape and general structure of the absorbent layer.

Turning to the accompanying photomicrographs, it can be seen that with the polymer film employed in the examples the approximate size of the pores, assuming elliptical shapes and spherical shapes, is for the elliptical shapes approximately 0.00009 inch X 0.00003 inch as the smallest size to 0.0005 inch x 0.0005 inch for the largest size, and 0.00001 inch for the diameter of the smallest to 0.001 inch for the largest.

A porous surface coating or layer having a pore volume of at least about 0.09 cubic inch per cubic inch of coating is usually required for adequate performace. The volume of open pores per cubic inch of treated surface in the polymer film shown in the photomicrographs is approximately 0.195 cubic inch/cubic inch of treated surface. FIG. 1 is the polymer film at X 1020 magnification. FIG. 2 is the polymer film at X 2040 magnification. FIG. 3 is the polymer film at X 5100 magnification.

The transfer elements of the invention are formed by coating the porous base polymer films with a compatible relatively non-volatile polar vehicle based ink. By-

compatible, it is meant that the ink does not appreciably dissolve or disrupt the porous polymeric structure of the base film surface.

The inks useful in the transfer elements of the invention comprise at least one colorant, that is either a dye or pigment or any combination of two or more thereof, including virtually all of the oil soluble dyes or pigments conventionally employed in the ink art, dispersed in a dispersant or vehicle.

The vehicle comprises at least one liquid polar organic compound which has a relatively low vapor pressure, preferably a vapor pressure less that about 1.0 mm of Hg at 20C., and most preferably a vapor pressure less than about 0.5 mm of Hg at 20C. The preferred vehicles are glycols, glycol ethers, alcohols, and fatty acids. The preferred glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and dipropylene glycol. The preferred glycol ethers include the monomethyl, monoethyl or monobutyl ethers of ethylene glycol, diethylene glycol mono methyl ether, dipropylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and propylene glycol monoethyl ether. The preferred alcohols include C to C monoalcohols including aliphatic alcohols such as cetyl alcohol, myristyl alcohol, stearyl alcohol, and alcohols derived from linoleic and linolenic acids. Oleyl alcohol is a particularly preferred alcohol. The fatty acids include C to C fatty acids and then glyceride oils invcluding stearic acid, palmitic acid, lauric acid, linoleic acid, cotton seed oil, soya oil, coconut oil, corn oil, and caprylic acid. Oleic acid is a particularly preferred acid.

The colorants which can be employed include azo dyes, including basic, acid, or metal complex azo dyes, including Bismark Brown (C.l. 331), Sudan Red G (C.l. 113) and Zapon Fast Yellow; the azine dyes, such as Safrin T (C.l. 841) and the indulines (e.g., Spirit lndulinc Cl. 860), the nigrosines (e.g., nigrosine C.l. 864) and the anilines (e.g., Aniline Black C.l. 8 70); triphenylmethane type, including Spirit Blue (C.l. 689), Xanthene type, including Methyl Eosine (CE. 769); anthraqumone type, including Sudan Violet R, Sudan Blue GL and Sudan Green BB; and Spirit soluble phthalocyanine dyes. Pigments such as carbon black or other insoluble inorganic colorants, may be employed either alone or in combination with a dye. Examples of such colorants include chrome yellow, copper phthalocyanine, iron blue and the like.

A presently preferred colorant comprises a nigrosine base colorant admixed with a fatty acid developer, preferably oleic acid; the fatty acid may also serve as the vehicle or may be used in conjunction with other vehicles such as, for example, oleyl alcohol.

The colorant is dispersed or dissolved in the vehicle. The exact proportions can be yaried depending on the materials employed, the desired print intensity, the type of equipment employed and the nature of the absorbent material printed upon. These are all parameters customarily dealt with by the routineer in the art and a particular product for a particular use can readily be formulated. The minimum amount of colorant employed is that amount necessary to provide a readable print upon transfer. The maximum amount of colorant employed is that amount which can be admixed with the vehicle and yet provide a pressure flowable transferablc inkfUsually the ink or image forming mixture contains from about to about 40 percent by weight of the ink mixture of a colorant; and the ink mixture usually contains from about 60 to about 85 percent by weight of the vehicle dispersant,

The transfer elements of this invention are prepared by coating the porous matte finish base polymer film with a substantially uniform coating of ink to provide a transfer element having substantially uniformly distributed across the surface and retained therein a pressure expressible mixture comprising a compatible relatively non-volatile, polar vehicle based ink.

One presently preferred method for applying the ink to the porous polymer film surface is with the use of an anilox flexographic system in single or multiple passes. Other methods include reverse roll coating, knife overroll, gravure, offset, letter press print coater, strip coater, and dip coating. The ink may be spread by a draw bar or by the use of a doctor blade. Any coating method which causes a substantially uniform coating to be retained on and within the porous base film surfaces can be utilized.

Where the ink is too viscous to be uniformly applied efficiently by a particular method, the ink may be diluted to suitable coating viscosity by volatile organic solvents or diluents which do not adversely effect the porous nature. of the base film. Examples of such solvents include methyl alcohol, ethyl alcohol, N-propyl alcohol, N-butanol, secondary butyl alcohol, monoethyl ether of ethyleneglycol, isopropyl alcohol, hexane, and Textile Spirits. After the diluted ink is applied, the solvent is evaporated either at ambient temperature or preferably at slightly elevated temperature to leave the relatively non-volatile ink composition retained on the surface of the porous polymer base film.

The amount of ink applied to the surface of the base polymer film is an amount which can be retained by the porous surface. The minimum amount of inkthat can be employed is that amount which is necessary to provide a uniform coating which is pressure expressible from the base film and by an applied pressure to provide a readable printed character. Generally, at least about 1.25 grams of ink are employed per square meter of polymeric base film surface. Usually from about 4 grams to 7 grams of ink are employed per squaremeter of the polymeric base film surface.

There follows several examples which describe embodiments of the invention. These examples should be considered illustrative rather than limiting. All parts andpercentages in the examples, as throughout the specification, are by weight unless otherwise specified.

All, temperatures are degrees Fahrenheit unless other wise. specified.

EXAMPLE I Table l shows ink formulations suitable for forming the transfer elements of the invention. The inks were formed by admixing the components.

TABLE l-Continued lNK COMPOSITIONS 1 (Parts by Weight) lnk Nigro- Oleie Carbon Oleyl Dipropylene No. sine Acid Black Alcohol Glycol EXAMPLE ll lnk Nigro- Oleylic Oleic *Monoethyl Ether of No. sine Alcohol Acid Ethylene Glycol The aged inks were diluted with the listed proportions of monoethyl ether of ethylene glycol for coating and additional viscosity control.

EXAMPLE 111 One mil Eve polystyrene synthetic paper (NCR) Appleton Paper Div.), as described above and in the accompanying photomicrographs, was coated in one pass using a hand held 180 cell per inch anilox flexographic proofer with each of the inks of Examples 1 and 11. In each case, a transfer element useful for printing was formed.

To demonstrate the effectiveness of the transfer element', a portion of each of the above transfer elements was spliced into the commercial transfer element of an lntermec Table Model No. 8105 Label Printer (lnterface Mechanisms, 1nc.). This machine employed a vertical drum containing characters, such as price numbers and code prints which are to be printed. (1) The transfer element is interposed between this drum and hammer. (2) The imprint receiving paperis passed between the hammer and drum with the paper print surface toward the inked side of the ribbon.

The printing was conducted on a number of varying paper stocks and the reflectance measured. The reflectancy measured was diffusive reflectance at 9000 A (magnesium oxide considered the standard for 100 percent reflectance).

1n the following table paper stocks are designated as follows: a bond (A); a coated text (B); a lithostock (C); OCR Label (D); a cast coated paper (E), a C/l/S Label Stock (F). The results of the printing tests are as follows:

TABLE 111 Reflectance or More Readings) lnk No. Paper Stock 1 C 19.8 1 B 19.3 2 B 18.8 2 C 16.7 2* B 16.0 5 B 17.1 5 C 13.5 6 13 v1 7.6 6 C 16.3 5 B 16.9 2* C 16.5 2 E 19.7 1 E 57.8 1 l" E 35.0 1 1 E 59.0 12 B 5 4.7 12 E 51.4 13 B 21.2 13 E 22.5 20 B 26.0 20 A 16.0 21 B 26.2 21 E 27.0 22 A 1 1.0 22 B 23.0' 22 E 25.0 23 B 22.0 23 A 13.0 23 E 24.0 24 B 30.0 24 A 12.0 24 E 22.0 26 B 24.0 26 A 15.0 26 E 25.0 28(applied di- B 47.0

luted with ethyl eellosolve) 28(coated B 29.0

film heated at F. to remove solvent) Second printing from ribbon. "Coated with two passes.

The hammer energy of the printing device was increased by printing only one-third the normal print area. The reflectance of these prints were compared with prints from the same transfer element, on the same stock, where the usual print area was printed. 1n all cases readable prints of numerics were achieved. Scannable Monarch Bar Code Prints have also been produced.

TABLE lv c6 nnued TABLE Vl-Continued Paper Stock Reflectance Ink Formula lnk Reflectance lnk No. Paper Stock 7 10 A, 17s 22 19.0 10 B 20.5 5 2s 17.0 23. 17.5 "Coated by two passes. 33*? I 27* 24.0

All prints described in Table IV on Stock .A were Ink formula diluted with monoethyl other of ethylene glycol as described in printed only one-third m l print are?" l0 ;i: f 0 r:l' lll|adliUlC( i with ethyl ccllosolvc as described in Example ll and adoublc The weight of the ink applied to the base film by the coating was lw above described method is shown by the following bl where the weight, in grams, is weight Square In the above examples other materials, such as those meter f base ffl described hereinabove, may [be substituted for those TABLE is exemplified to achieve. results within the scope of this invention. Likewise, the proportions of the materials employed may be varied as described above. While the Ink image receiving material exemplified. ispaper, other 27 977 (excess ink on surface) ink absorbent image receiving materials may be used as 33 6.96 image receiving material. 24 We claim: 31 4.44 30" 4.88 1. An image producing transfer element comprising 53 i}: a. an alkenyl aromatic resinous film having a porous 20 ink receptlve alkenyl aromatic reslnous matter sur- 22 6.07 25 face, 26 b. said resinous film having substantially uniformly 21 5.71 I 25" 1.44 distributed across its matte surface and retained therein a pressure expressible ink comprising a colorant dispersed in a relatively non-volatile polar ve- Coated with two passes. 30 hicle. "*One part ink diluted with one part monocthyl ether ofethylcnc glycol by weight. 2 A transfer element, as i l i 1 h i h cop Two parts ink diluted with one part ethyl ccllosolve by weight. orant s HigFOSiIIB or 3 C ination f nigl' sil'le a fatty acid. 3. A transfer element, as in claim 2, wherein the polar EXAMPLE Iv vehicle is selected from the group consisting of glycols,

One mil Eve polystyrene synthetic paper (NCR Apglycol ethers, alcohols and fatty acids or mixtures pleton Paper Div.) as described above and in the acthereof. companying photomicrographs, wa ated in ne o 4. A transfer element, as in claim 1, wherein the alkemultiple passes using a hand held 180 cell per inch nyl r matic resinous film is polystyrene. flexographic proofer with each of the inks of Examples 40 A transfer element, as in daim wherein the and II, In h Case, a transfer element f f orant is nigrosine or a combination of nigrosine with a printing was formed. fatty acid.

Again, to demonstrate the effectiveness of the trans- A transfer ehimehtr as in Claim 4, wherein the Polar fer element, a portion of each of the listed transfer ele- Vehicle is Selected from the group consisting of glycols, ments was spliced into the commercial transfer element g y ethers, alcohols and fatty acids or mixtures ofa Monarch Model 2001 Bar Code Printer. The Monthereofarch Model 2001 is a free standing computer-line A transfer element, as in claim wherein the P printer. Prints are made by firing a solenoid activated Surface is at least about cubic inch P cubic 'hammer against a horizontal drum containing characinch of PorouS Coatingters and Code Bars to be printed. A transfer element A transfer elerhentr as in Claim wherein the transfers ink by passing next to the drum with the ink transferelement retains at least. about 1.25 grams ofink surface facing a tag or label which is struck in a ham- F P P Square meter alkenyl aromatic mer driving the materials together with enough force to nous mtransfer ink in the shape of the drum character con- An Image Prduclr1g trfmsfer elemen? comPnsmg tacted. Printing was made on a 10 pt. (10 mil) tag stock alkenylaromaflc resmous film havmg a Pomus used in Monarch Computer tags. Scannable Bar Code mk receptwe resmous Polymer surface Prepared Prints were produced on a Monarch Model 2001 drum from a Process Compnsmg treatmg the surface of printer with the listed ink formulations. (Other formu a fi P from an alkfiflyl aromatfc l lations described herein are also used.) The reflectancy h m a volaule g measured was diffuse reflectance at 9000 A (magne- 0 hquld 'T' swelhflg agent f .sium oxide considered the standard for 100 percent rekeny] aromanc f Swellmg agent 'L f' iflectance) tween about 40 centlgrade and about 135 centlgrade, the film being contacted with the treating TABLE VI medium within a temperature range of from about 0 to about 60 Centigrade, said mixture having dislnk Formula Paper Stock ink Reflectance persed therein from about 0.05 percent to about 5 30H 10 PL mg percent by weight of an ink receptive resinous pol- 24 21.0 ymeric material, unitl the surface of said film IS swollen by said swelling agent and subsequently removing by evaporation the volatile component of said mixture from said film to form a porous matte surface on said polymer resin film,

b. said resinous polymer film having substantially uniformly distributed across its matte surface and retained therein a pressure expressible ink comprising a colorant dispersed in a relatively non-volatile polar vehicle.

10. A transfer element, as in claim 9, where the swelling agent comprises acetone.

11. A transfer element, as in claim 9, where the ink receptive polymeric material is a copolymer of vinylidene chloride and acrylonitrile.

12. A transfer element, as in claim 9, where the ink receptive polymeric material is nitrocellulose.

13. A transfer element, as in claim 9, where the ink receptive polymeric material is a polyvinyl acetal resin.

14. A transfer element, as in claim 9, where the ink receptive polymeric material is a polyester resin.

15. A transfer element, as in claim 9, where the ink receptive polymeric material is employed in a proportion of from about 0.1 to about 2 percent by weight of the treating mixture.

16. A transfer element, as in claim 9, wherein the alkenyl aromatic resinous film is polystyrene.

17. A transfer element, as in claim 9, wherein the colorant is nigrosine or a combination of nigrosine with a fatty acid.

18. A transfer element, as in claim 9, wherein the polar vehicle is selected from the group consisting of glycols, glycol ethers, alcohols and fatty acids or mixtures thereof.

19. A transfer element, as in claim 9, wherein the porous surface is at least about 0.09 cubic inch per cubic inch of porous coating.

20. A transfer element, as in claim 19, wherein the transfer element retains at least about 1.29 grams of ink composition per square meter of alkenyl aromatic res- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,90 3 DATED September 23, 1975 9 'NVENTOR(5 1 WILLIAM LEE ROSENDALE AND ARDYTH' DALE LAKES It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In claim 1, column 10, line 23, delete "matter" and '8 insert matte Signed and Scaled this Fourth Day of April 1978 I [SEAL] Arrest:

I Rl'TH MASON l.l"lRl-lLLF, F. PARKER I Arresting Officer Acting Commissioner of Patents and Trademarks 

1. AN IMAGE TRANSFER ELEMENT COMPRISING A. AN ALKENYL AROMATIC RESINS FILM HAVING A POROUS INK RECEPTIVE ALKENYL AROMATIC RESINOUS MATTER SURFACE, B. SAID RESINOUS FILM HAVING SUBSTANTIALLY UNIFORMLY DISTRIBUTED ACROSS ITS MATTE SURFACE AND RETAINED THEREIN A PRES-
 2. A transfer element, as in claim 1, wherein the colorant is nigrosine or a combination of nigrosine with a fatty acid.
 3. A transfer element, as in claim 2, wherein the polar vehicle is selected from the group consisting of glycols, glycol ethers, alcohols and fatty acids or mixtures thereof.
 4. A transfer element, as in claim 1, wherein the alkenyl aromatic resinous film is polystyrene.
 5. A transfer element, as in claim 4, wherein the colorant is nigrosine or a combination of nigrosine with a fatty acid.
 6. A transfer element, as in claim 4, wherein the polar vehicle is selected from the group consisting of glycols, glycol ethers, alcohols and fatty acids or mixtures thereof.
 7. A transfer element, as in claim 4, wherein the porous surface is at least about 0.09 cubic inch per cubic inch of porous coating.
 8. A transfer element, as in claim 7, wherein the transfer element retains at least about 1.25 grams of ink composition per square meter of alkenyl aromatic resinous film.
 9. An image producing transfer element comprising a. an alkenyl aromatic resinous film having a porous ink receptive resinous polymer surface prepared from a process comprising treating the surface of a film prepared from an alkenyl aromatic polymer resin with a mixture comprising a volatile organic liquid medium which is a swelling agent for said alkenyl aromatic resin, said swelling agent boiling between about 40* centigrade and about 135* centigrade, the film being contacted with the treating medium within a temperature range of from about 0* to about 60* centigrade, said mixture having dispersed therein from about 0.05 percent to about 5 percent by weight of an ink receptive resinous polymeric material, unitl the surface of said film is swollen by said swelling agent and subsequently removing by evaporation the volatile component of said mixture from said film to form a porous matte surface on said polymer resin film, b. said resinous polymer film having substantially uniformly distributed across its matte surface and retained therein a pressure expressible ink comprising a coloRant dispersed in a relatively non-volatile polar vehicle.
 10. A transfer element, as in claim 9, where the swelling agent comprises acetone.
 11. A transfer element, as in claim 9, where the ink receptive polymeric material is a copolymer of vinylidene chloride and acrylonitrile.
 12. A transfer element, as in claim 9, where the ink receptive polymeric material is nitrocellulose.
 13. A transfer element, as in claim 9, where the ink receptive polymeric material is a polyvinyl acetal resin.
 14. A transfer element, as in claim 9, where the ink receptive polymeric material is a polyester resin.
 15. A transfer element, as in claim 9, where the ink receptive polymeric material is employed in a proportion of from about 0.1 to about 2 percent by weight of the treating mixture.
 16. A transfer element, as in claim 9, wherein the alkenyl aromatic resinous film is polystyrene.
 17. A transfer element, as in claim 9, wherein the colorant is nigrosine or a combination of nigrosine with a fatty acid.
 18. A transfer element, as in claim 9, wherein the polar vehicle is selected from the group consisting of glycols, glycol ethers, alcohols and fatty acids or mixtures thereof.
 19. A transfer element, as in claim 9, wherein the porous surface is at least about 0.09 cubic inch per cubic inch of porous coating.
 20. A transfer element, as in claim 19, wherein the transfer element retains at least about 1.29 grams of ink composition per square meter of alkenyl aromatic resinous film. 